Flow field control over a high-aspect-ratio wing using a plasma actuator at low Reynolds number

In order to improve the takeoff performance of Unmanned Aerial Vehicles (UAVs) in plateau, the studies of flow control over a wing with high aspect ratio using a single symmetrical layout of dielectric barrier discharge plasma actuator were carried out with the help of wind tunnel experiments and numerical simulation at low Reynolds number. The flow control effect was evaluated and the flow control mechanism was revealed. Interestingly, the laminar trailing-edge separation vortex at low angle of attack and the stall separation flow at high angle of attack can be suppressed by one symmetrical plasma actuator. The results indicate that the variation of wing aerodynamics with angle of attack conforms to the characteristics of low Reynolds number aerodynamics at the Reynolds number of 7.47×10⁴ before plasma actuation. The lift coefficient increases nonlinearly, while the drag coefficient first increases, then decreases, and then increases again. It should be noted that the trailing-edge separation vortex is the underlying mechanism of nonlinear aerodynamic phenomena. Regarding the aerodynamics control effectiveness of plasma, the aerodynamic performances of wing can be enhanced by the symmetrical plasma actuator over a wide range of angles of attack. At low angles of attack, the phenomena of aerodynamic nonlinearity were eliminated almost and the maximum lift to drag ratio was increased by about 15% by the plasma actuator. At high angles of attack, stall separation flow around the wing was suppressed and the stall angle is delayed by about 2°. Regarding the mechanism of plasma flow control, the induced vortices of symmetrical plasma actuator play an important role in achieving flow control over a wide range of angles of attack. The induced vortices transferred the momentum from the leading edge to the trailing edge of airfoil and squeezed the laminar separation bubble when controlling the trailing-edge separation vortex. When applied to the control of flow separation at high angle of attack, the induced vortices enhanced the mixing between high-energy mainstream and low-energy boundary layer airflow and suppressed the stall separation flow by integrating the large-scale separation vortices at high angles of attack.